Alkyl-aryl sulfoxides in photoinitiating process and product

ABSTRACT

The present invention relates to a photopolymerization process comprising irradiating a photopolymerizable material with U.V. light of wave length 250 to 400 nm in the presence of a photosensitizing amount of a photoinitiator of formula I, ##STR1## in which R is hydrogen or halogen 
     R 1  is alkyl, cycloalkyl, benzyl, optionally substituted phenyl or (a) ##STR2##  either R 2  is optionally substituted alkyl, benzyl, C 6  H 5  --CH═CH--, 2-thienyl, 2-furyl, 2-(3-chloro)benzothienyl or optionally substituted phenyl, and 
     R 3  is hydrogen or R 2  and R 3  form a radical of formula (b) ##STR3##  in which X is a direct bond, --O--, --S--, --CH 2  --, ##STR4##  and R 4  and R&#39; have one of the significances of R 2  and R, respectively, 
     with the proviso that when R 1  is (a) R 3  is hydrogen and R 2  and R 4  are free from halogen atoms.

The present application is a continuation-in-part application of application Ser. No. 49 572 filed June 18, 1979 and now abandoned.

The present invention relates to a photopolymerization process and photopolymerizable compositions.

More particularly, the present invention provides a photopolymerization process comprising irradiating a photopolymerizable material with U.V. light of wave length 250 to 400 nm in the presence of a photosensitizing amount of a photoinitiator of formula I, ##STR5## in which R is hydrogen or halogen,

R₁ is (C₁₋₁₈)alkyl, (C₅₋₈)cycloalkyl, benzyl, phenyl, phenyl substituted by up to two (C₁₋₄)alkyl groups or a group of formula (a) ##STR6## either R₂ is (C₁₋₂₁)alkyl; (C₁₋₂₁)alkyl substituted by up to 3 halogen atoms; (C₁₋₄)alkoxy(C₁₋₆) alkyl; benzyl; (C₁₋₄)alkyl substituted by a tertiary amino group; C₆ H₅ CH═CH--, 2-thienyl, 2-furyl or 2-(3-chloro)benzothienyl; phenyl optionally substituted by up to three substituents selected from the group consisting of (C₁₋₁₂)alkoxy, (C₁₋₁₂)alkyl (max. 3 of each) halogen atoms (a maximum of two), hydroxy and (C₁₋₈)alkyl ester (maximum of 1 of each of these) with the proviso that the total number of carbon atoms in all the substituents taken together is at most 12, and

R₃ is hydrogen,

or R₂ and R₃ together form a radical of formula (b) ##STR7## in which X is a direct bond, --O--, --S--, --CH₂ --, ##STR8## and in which the carbon atom marked with the asterisk is bound to the >C═O group,

R' has one of the significances of R and

R₄ has one of the significances of R₂ except where R₂ and R₃ form a group of formula (b),

with the proviso that when R₁ is a group of formula (a) R₃ is hydrogen and R₂ and R₄ are free from halogen atoms.

Any halogen in the compounds of formula I is preferably chlorine or bromine, more preferably chlorine.

Preferably R and R' are halogen only when R₁ is optionally substuted phenyl or group (a). Any halogen is preferably chlorine. Preferably R and R' are the same. Most preferably both R and R' are hydrogen.

Any phenyl as R₁ is preferably unsubstituted or monosubstituted.

Where R₃ is hydrogen R₁ is preferably R₁ ', where R₁ ' is (C₁₋₁₈)alkyl, benzyl, phenyl which is optionally substituted by up to two (C₁₋₄)alkyl groups or a group of formula (a). More preferably R₁ is R₁ ", where R₁ " is (C₁₋₁₂) alkyl, benzyl, phenyl or (C₁₋₄)alkylphenyl or a group of formula (aa) ##STR9## wherein R₄ ' is defined below. Most preferably R₁, when R₃ is hydrogen, is R₁ '", where R₁ '"is (C₁₋₁₂)alkyl or phenyl, particularly alkyl, with methyl, propyl, butyl, hexyl and octyl being especially preferred, most especially methyl.

Any alkyl as R₁ or R₁ ', where R₃ is hydrogen, preferably contains 1 to 12 more preferably 1 to 8 carbon atoms.

When R₂ and R₃ form a group of formula (b) R₁ is preferably R_(1X), where R_(1X) is (C₁₋₁₈)alkyl, benzyl or phenyl, more preferably R₁ is R_(1X) ', where R_(1X) ' is (C₁₋₁₈)alkyl or phenyl. Even more preferably R₁ is R_(1X) ", where R_(1X) " is (C₄₋₁₈)alkyl or phenyl, with alkyl, especially C₄₋₁₂ alkyl, more especially (C₄₋₈)alkyl, being most preferred.

Any alkyl as R₁, R_(1X) or R_(1X) ', when R₂ and R₃ form a group of formula (b), preferably contains 4 to 18, more preferably 4 to 12 and most preferably 4 to 8 carbon atoms.

Any alkyl as R₂ and/or R₄ which is substituted by a tertiary amine is preferably (alkyl(C₁₋₄))₂ N-alkylene(C₂₋₄)-, ##STR10##

R₂ is preferably R₂ ', where R₂ ' is either (C₁₋₂₁)alkyl; (C₁₋₂₁)alkyl substituted by up to three halogen atoms; (C₁₋₄)alkoxy-(C₁₋₆)alkyl; 2-thienyl,2-furyl or 2-(3-chloro)benzothienyl; phenyl optionally substituted by up to three substituents selected from the group consisting of (C₁₋₁₂)alkyl, (C₁₋₁₂)alkoxy (maximum of three of each of these) halogen atoms (maximum of two thereof) and (C₁₋₈)alkylester (maximum of one of these) with the proviso that the total number of carbon atoms in the combined substituents is at most 12 or R₂ ' together with R₃ forms a group of formula (b).

More preferably R₂ is R₂ ", where R₂ " is either (C₁₋₂₁)alkyl; (C₁₋₂₁)alkyl substituted by up to three halogen atoms, phenyl; phenyl substituted by a total of up to three substituents selected from (C₁₋₁₂)alkyl (C₁₋₁₂)alkoxy (maximum of three of each), halogen atoms (maximum of two of these) and (C₁₋₈)alkylester (maximum of one of these) with the proviso as stated above for R₂ '; 2-thienyl or 2-furyl or R₂ " with R₃ forms a group of formula (b). Even more preferably R₂ is R₂ '", where R₂ '" is either (C₁₋₁₂) alkyl, phenyl or phenyl substituted by up to two (C₁₋₉) alkyl groups with the proviso that the total number of carbon atoms in said combined substituents is at most 9 or R₂ '" with R₃ forms a group of formula (b) where X is X'" as defined below. Yet even more preferably R₂ is R₂ ^(iv), where R₂ ^(iv) is (C₁₋₄)alkyl, phenyl, monoalkyl(C₁₋₄)phenyl. Most preferably R₂ is R₂ ^(v) where R₂ ^(v) is methyl, ethyl, propyl, phenyl and para-tert.butyl-phenyl with methyl or phenyl being especially preferred, particularly phenyl.

When R₂, R₂ ', R₂ " is alkyl such alkyl preferably contains 1 to 18, more preferably 1 to 12, even more preferably 1 to 8 and most preferably 1 to 4 carbon atoms with (C₁₋₃)alkyl, preferably methyl, being especially preferred.

When R₂, R₂ ', R₂ " or R₂ '" is phenyl preferably such phenyl is unsubstituted or monosubstituted especially by an alkyl group, with unsubstituted phenyl being most preferred.

When R₂ or R₂ ' is a heterocyclic group 2-thienyl and 2-furyl are preferred especially 2-furyl.

R₃ is preferably hydrogen.

X is preferably X' where X' is a direct bond, --O--, --S--, --CH₂ -- or --CO--. More preferably X is X" where X" is --O--,--CH₂ --, --S-- or --CO--. Most preferably X is X'" where X'" is O, --S-- or --CO--, especially --CO-- and --S--, particularly --CO--.

When R₁ is a group of formula (a) R₄ is preferably R₄ ', more preferably R₄ ", even more preferably R₄ '", yet even more preferably R₄ ^(iv), most preferably R₄ ^(v) where R₄ ', R₄ ", R₄ '", R₄ ^(iv) and R₄ ^(v) has one of the sigificances of R₂ ', R₂ ", R₂ '", R₂ ^(iv) and R₂ ^(v), respectively, with the exclusion of the cases where R₂ and R₃ form a group of formula (b). Most preferably R₄ and R₂ are identical with the exclusion of the case where R₂ and R₃ form a group of formula (b).

Preferred photoinitiators in the process of the present invention are those of formula I, wherein R₁ is R₁ ' or R_(1X), R₂ is R₂ ' and when R₁ ' is a group of formula (a) R₄ is R₄ ' and when R₂ and R₃ together form a group of formula (b), X is X' and any halogen as R and/or R' is chlorine.

More preferred photoinitiators are those of formula Ia, ##STR11## in which R_(1a), when R₃ is hydrogen, is R₁ " as defined above, and when R₃ is part of the group of formula (b), R_(1a) is R_(1X) ' as defined above, and X is X', preferably X".

Of the compounds of formula I and Ia those which are free from halogen atoms are preferred.

Most preferred photoinitiators are those of formula Ib, ##STR12## in which R₁ '" is as defined above and

R₂ '" is as defined above except for radical (b).

The present invention further provides compounds of formula Ix, ##STR13## in which R₁ is defined above, and when R₁ is a group of formula (a), as defined above, R₄ has one of the significances of R₂ as defined above and R and R' are as defined above,

either

R_(2x) is 2-thienyl, 2-furyl or 2-(3-chloro)benzothienyl; or phenyl optionally substituted by up to three substituents selected from the group consisting of (C₁₋₁₂)alkyl (C₁₋₁₂)alkoxy, (maximum of three of each) halogen atoms (a maximum of two), hydroxy and (C₁₋₈)alkyl ester (maximum of 1 of each of these) with the proviso that the total number of carbon atoms in all the substituents taken together is at most 12, and R₃ is hydrogen

or

R_(2x) and R₃ together form a group of formula (b) as defined above

with the proviso that, when X is a direct bond or --CO--, R₁ is other than methyl.

Preferred compounds of formula Ix, are those where R_(2x) is optionally substituted phenyl or with R₃ forms a group of formula (b). More preferred compounds of formula Ix are those in which R_(2x) is phenyl optionally substituted by up to two (C₁₋₉)alkyl groups with the proviso that the total number of carbon atoms in the combined substituents is at most 9, or R_(2x) together with R₃ forms a group of formula (b) where X is X", R₁ is R₁ ' or R_(1X), preferably R₁ " or R_(IX) ', and R and R' are both hydrogen. Most preferred compounds are those where R_(2x) is phenyl or mono(C₁₋₄)alkylphenyl or with R₃ forms a group of formula (b) where X is X'", R₁ is R₁ '" and R is hydrogen, especially those where R₃ is hydrogen.

The present invention also provides a process for the production of compounds of formula Ix, as defined above, comprising oxidizing a compound of formula II ##STR14## to form a sulphoxide.

The oxidation reaction may be effected in accordance with known methods. Examples of suitable oxidizing agents are H₂ O₂ and meta-chloroperbenzoic acid.

The compounds of formula I which do not fall within formula I_(x) are either known or may be prepared in accordance with known methods from available starting materials.

The compounds of formula II may be prepared in accordance with conventional methods.

The present invention also provides photopolymerizable systems comprising a photopolymerizable substance in conjunction with a photosensitizing amount of a compound of formula I. Such photopolymerizable substances in said systems and employed in the photopolymerization process of the invention are known e.g. in the ultraviolet curable coating and printing ink arts. Preferred photopolymerizable substances are those which contain unsaturated compounds. Such systems may also contain other additives such as antioxidants, pigments and fillers. The exact amount of such substances is not critical and will vary depending on the use for which the polymerized material is designed.

One advantage of a photopolymerisable system and process of the present invention is that it is not necessary to use coinitiators such as amines which contain an α-CH-group in the process or in the system. Such amines are known in the art.

Similarly, the amount of the photoinitiator will depend on the ultimate use for which the polymerized material is designed. In general it is sufficient to employ 0.01 to 10, preferably 0.05 to 5% by weight based on the polymerizable formulation.

Finally, the present invention additionally provides a composition for effecting photopolymerization when added to a photopolymerizable material comprising a compound of formula I in admixture with an epoxidized compound. Suitable epoxidized compounds include epoxidized linseed oil. These compositions may contain up to 90% initiator.

The photopolymerization process and the photopolymerizable systems of the present invention are particularly useful in the formation of thick layers and in the formation of white pigmented systems.

The following Examples further serve to illustrate the invention. In the Examples all parts are by weight and the temperatures are in degrees Centigrade.

EXAMPLE 1

11.4 g of 4-benzoyl thioanisole are dissolved in 100 g glacial acetic acid at 10°-21°. With a little stirring the solution is reacted over a period of 15 minutes with 4.25 g of 30% H₂ O₂. The mixture is then left to stand for 6 hours and subsequently poured onto 25 ml ice water. The precipitate is suction filtered, washed with water, dried and recrystallized from methanol. A white crystalline product, melting point 87° to 88° of formula ##STR15## is obtained.

EXAMPLE 2

Proceeding in analogous manner to that described in Example 1 but oxidizing 4-benzoyl diphenylsulphide a white crystalline product, melting point 73° to 76° of formula ##STR16## is obtained.

EXAMPLE 3

Proceeding in analogous manner to that described in Example 1 but oxidizing 4-p-tert-butyl-benzoyl diphenylsulphide a white crystalline product, melting point 144° to 146° of formula ##STR17## is obtained.

EXAMPLE 4

When 4-o-methylbenzoyl diphenylsulphide is oxidized, in analogous manner to the procedure described in Example 1, a resin of formula ##STR18## is obtained.

EXAMPLE 5

5,7 g of 2,2'-dichloro-4,4'-(tert.butyl-benzoyl) diphenylsulphide are put into 15 ml glacial acetic acid/glacial acetic acid anhydride (60:40) at 40° and are reacted with 0.85 g H₂ O₂ (40%) over a period of 30 minutes, whereby a clear solution is obtained. After 4 hours stirring a further 0.85 g H₂ O₂ are added and the solution is stirred for further 4 hours at the same temperature. Subsequently the solution is poured onto 200 ml ice water at 5° whereupon the reaction product precipitates. The precipitate is suction filtered, washed with water and dried. A white product, melting point 84° to 94° of formula ##STR19## is obtained.

EXAMPLES 6-49

Proceeding in analogous manner to that described in Example 5 and oxidizing 2,2'-dichloro-4,4'-dibenzoyl diphenylsulphide a white crystalline product, melting point 114° to 117° of formula ##STR20## is obtained.

The compounds of the following Table 1 are prepared in analogous manner to the procedures of Examples 1 to 6.

                                      TABLE 1                                      __________________________________________________________________________      ##STR21##                                                                     Example                                                                        No.  R.sub.2    R.sub.1         m. pt. °C.                              __________________________________________________________________________     7    CH.sub.3   CH.sub.3                                                       8    C.sub.2 H.sub.5                                                                           CH.sub.3                                                       9    CH.sub.3   C.sub.8 H.sub.17                                               10   C.sub.11 H.sub.23                                                                         CH.sub.3                                                       11   C.sub.8 H.sub.17                                                                          C.sub.8 H.sub.17                                               12                                                                                   ##STR22## C.sub.8 H.sub.17 (n)                                                                           ˜38                                      13                                                                                   ##STR23## CH.sub.3        102/103                                        14                                                                                   ##STR24## CH.sub.3        135-136                                        15                                                                                   ##STR25## CH.sub.3        84-85                                          16                                                                                   ##STR26## CH.sub.3          148-149.5                                    17                                                                                   ##STR27## C.sub.8 H.sub. 17                                              18                                                                                   ##STR28## CH.sub.3        130-131                                        19                                                                                   ##STR29## CH.sub.3                                                       20                                                                                   ##STR30##                                                                                 ##STR31##                                                     21                                                                                   ##STR32##                                                                                 ##STR33##                                                     22                                                                                   ##STR34## CH.sub.3                                                       23                                                                                   ##STR35## CH.sub.3        resin                                          24                                                                                   ##STR36## CH.sub.3                                                       25                                                                                   ##STR37## CH.sub.3                                                       26                                                                                   ##STR38## CH.sub.3                                                       27                                                                                   ##STR39## CH.sub.3        105                                            28                                                                                   ##STR40## CH.sub.3        116-117                                        29                                                                                   ##STR41## C.sub.12 H.sub.25                                                                              resin                                          30                                                                                   ##STR42## CH.sub.3        125-126                                        31                                                                                   ##STR43## CH.sub.3        135-136                                        32                                                                                   ##STR44## C.sub.4 H.sub.9 79-80                                          33                                                                                   ##STR45## CH.sub.3        134-135                                        34                                                                                   ##STR46## C.sub.4 H.sub.9 (n)                                                                            resin                                          35                                                                                   ##STR47## CH.sub.3        150-151                                        36                                                                                   ##STR48## CH.sub.3        188-189                                        37                                                                                   ##STR49## CH.sub.3        resin                                          38                                                                                   ##STR50##                                                                                 ##STR51##      90-92                                          39                                                                                   ##STR52##                                                                                 ##STR53##      92-95                                          40                                                                                   ##STR54## CH.sub.3        83-84                                          41   (CH.sub.3).sub.3 C                                                                        CH.sub.3        86.5-87                                        42   (CH.sub.3).sub.2 CH                                                                       CH.sub.3          71-71.5                                      43                                                                                   ##STR55##                                                                                 ##STR56##      151-152                                        44                                                                                   ##STR57##                                                                                 ##STR58##      103.5-105                                      45                                                                                   ##STR59## C.sub.4 H.sub.9 (n)                                                                            82-83                                          46                                                                                   ##STR60## C.sub.4 H.sub.9 (t)                                                                            57- 58                                         47                                                                                   ##STR61## C.sub.4 H.sub.9 (?)                                                                            90-92                                          48   (CH.sub.3).sub.2 CH                                                                        ##STR62##      89-90                                          49                                                                                   ##STR63##                 resin                                          __________________________________________________________________________

EXAMPLE 50

1.2 g 3-n-octylmercapto-thioxantone are dissolved in 50 ml glacial acetic acid at 50°. The solution is reacted with 0.12 ml H₂ O₂ (30%) and left to stand at 50° for 20 hours. Then the solution is poured onto 100 ml ice water, whereupon the product precipitates. The precipitate is suction filtered, washed with water, dried and recrystallized from methanol. A yellow crystalline product, melting point 95° to 96° of formula ##STR64## is obtained.

EXAMPLE 51

14.2 g 2-butyl-mercapto-anthraquinone (m.pt. 117°-119°) are dissolved in 200 ml glacial acetic acid at 50°. The solution is reacted with 4.25 g H₂ O₂ (30%) and stirred for 6 hours at 50°. Then a further 0.4 g H₂ O₂ are added and the mixture stirred for 16 hours. The mixture is poured onto 250 ml ice water whereupon the product precipitates. The precipitate is extracted with toluene. The solution is washed neutral and the solvent is distilled off. The yellow residue is recrystallised from methanol. A yellow product, melting point 97° to 98° of formula ##STR65## is obtained.

EXAMPLE 52

1.85 g 3-butyl-mercapto-xanthone (m.pt. 83°-84°) are dissolved in a mixture of 30 ml glacial acetic acid and 5 ml glacial acetic acid anhydride. Then the solution is reacted with 0.6 g H₂ O₂ and stirred for 41/2 hours at 20°. The solution is poured onto 100 ml ice water, further stirred for 15 minutes whereupon the product precipitates. The precipitate is suction filtered, washed neutral with water and dried. The product is recrystallized from methanol. A white crystalline product, melting point 128° to 130° of formula ##STR66## is obtained.

The compounds of the following Table 2 are prepared in analogous manner to the procedure of Examples 50 to 52.

                  TABLE 2                                                          ______________________________________                                          ##STR67##                                                                     Example                                                                        No.      X         R.sub.1        m.pt. °C.                             ______________________________________                                         53       S         C.sub.4 H.sub.9 (n)                                                                           112-113                                      54       CO                                                                                        ##STR68##     197-198                                      55       CO                                                                                        ##STR69##     174-176                                      56       CO        C.sub.12 H.sub.25                                                                             118-119                                      57       CO        C.sub.18 H.sub.37                                                                             111-120                                      ______________________________________                                    

APPLICATION EXAMPLE A

A mixture consisting of 70 parts EBECRYL 850 viscosity at 25° C. approximately 250 poise, mol.weight 1500 (a polyester acrylate prepolymer sold by UCB, Belgium) and 30 parts TiO₂ are thoroughly mixed in a roller mill. To this mixture 5% of the compound of Example 2 are added and are milled till the mixture is homogeneous. The composition is spread with a spatula in a thickness of 3 to 5μ on matt art paper and also spread on aluminium foile in a thickness of 20μ. Both films are dried in U.V. minicure apparatus (Primarc) with a mercury-medium pressure lamp (80 W/cm) at high speed until non-taky.

APPLICATION EXAMPLE B

A resin mixture consisting of 82 parts Plex 6624-0 (acrylic resin of Rohm, Darmstadt) and 18.0 parts Plex 6618-0 (acrylate based thinner, Rohm Darmstadt) and 5 parts of the compound of Example 5 are spread on matt art paper with a spatula in a thickness of 3 to 5μ. The film is dried to non-tackiness in a minicure apparatus as mentioned above in Application Example A.

APPLICATION EXAMPLE C

In analogous manner to the procedure of Example A two films, one of 3-5μ and the other of 20μ, were made employing 60 parts prepolymer of formula ##STR70## viscosity c. 9000 poise at 77° C. (see U.S. Pat. No. 3,713,864) 35 parts pentaerithriotoltetraacrylate and 40 parts TiO₂.

In analogous manner to the procedures described in Examples A and B and C above the compounds of Examples 1, 3, 4 and 6-57 are employed as photoinitiators. 

What is claimed is:
 1. A photopolymerization process comprising irradiating a photopolymerizable material with U.V. light of wave length 250 to 400 nm in the presence of a photosensitizing amount of a photoinitiator of formula I, ##STR71## in which R₁ is (C₁₋₁₂)alkyl, andeither R₂ '" is (C₁₋₂)alkyl, phenyl or phenyl substituted by up to two (C₁₋₉)alkyl groups with the proviso that the total number of carbon atoms in said combined substituents is 9,and R₃ is hydrogen,or R₂ '" and R₃ together form a radical of formula (b) ##STR72## in which X'" is --S-- or ##STR73## and in which the carbon atom marked with the asterisk is bound to the ##STR74## group in formula I.
 2. A process according to claim 1, in which R₂ '" is (C₁₋₄)alkyl, phenyl or monoalkyl(C₁₋₄)phenyl.
 3. A process according to claim 2, in which R₁ is methyl, ethyl, propyl, butyl, hexyl or octyl and R₂ '" is methyl, ethyl, propyl, phenyl or para tert. butylphenyl.
 4. A process according to claim 3, in which R₁ is methyl and R₂ '" is methyl or phenyl.
 5. A process according to claim 1, in which in the compound of formula I R₃ is hydrogen.
 6. A process according to claim 1, in which in the compound of formula I R₃ together with R₂ '" forms a radical of formula (b).
 7. A photopolymerisation process according to claim 1 in which the sole photoinitiator is that of formula I.
 8. A photopolymerisation process according to claim 1 in which the photoinitiator of formula I has the formula ##STR75## or the formula ##STR76##
 9. A photopolymerizable system comprising a photopolymerizable material in conjunction with a photosensitizing amount of a compound of formula I as defined in claim
 1. 10. A photopolymerizable system according to claim 9 in which the compound of formula I is present in an amount of 0.01 to 10% by weight based on the polymerizable formulation.
 11. A photopolymerisable system according to claim 9 comprising a photopolymerisable material in conjunction with a photosensitizing amount of a compound of formula I as sole photoinitiator.
 12. A process according to claim 6 wherein X'" is ##STR77##
 13. A process according to claim 2, 3, 4, 5, 6, 8, 1, or 12 wherein the amount of photoinitiator is 0.01 to 10% by weight of the photopolymerizable material. 